Protractor gives "Unable to start a WebDriver session" error

According to the relevant github issue, the problem is that chromedriver cannot find chrome browser executeable - on different operating systems it searches for it in different places.

You need to either have chrome installed where chromedriver expects it to be, or specify the path to the chrome executeable in the binary setting:

capabilities: {
    "browserName": "chrome",
    "chromeOptions": {
        binary: "D:/Program Files/Chrome/chrome.exe",
        args: [],
        extensions: [],
    }
},